Melanoma is a skin cancer that is caused by the oncogenic transformation of melanocytes, which are pigment producing skin cells. As of 2009, Melanoma had a prevalence of more than 870,000 cases in the US alone (US National Institutes of Health). Each year, over 75,000 new cases of melanoma are diagnosed in the US, and approximately 25% of patients have advanced disease at the time of diagnosis. Despite the fact that cases of primary melanoma can be cured by surgery if they are detected early enough, melanoma is the leading cause of death from skin disease in the US, responsible for about 10,000 deaths per year in the US. Once the disease has spread and became metastatic, the prognosis is poor, with a 5 year relative survival of 15%.
There are four basic types of melanomas. Three types are found in the top layers of the skin and the fourth one is invasive and has penetrated deeper into the skin and may have spread to other areas of the body.
Superficial spreading melanoma is the most common type of melanoma which accounts for about 70% of all cases. It grows along the top layer of the skin for a fairly long time before penetrating more deeply. It first appears as a flat or slightly raised discolored patch that has irregular borders and may be somewhat asymmetrical in form. The color varies, and you may see areas of tan, brown, black, red, blue or white. This type of melanoma can occur in a previously benign mole and is found most often in young people.
Lentigo maligna is similar to the superficial spreading type, as it also remains close to the skin surface for quite a while, and usually appears as a flat or mildly elevated mottled tan, brown or dark brown discoloration. It is found most often in the elderly. When this cancer becomes invasive, it is referred to as lentigo maligna melanoma.
Acral lentiginous melanoma also spreads superficially before penetrating more deeply. It is quite different from the others, though, as it usually appears as a black or brown discoloration under the nails or on the soles of the feet or palms of the hands. This type of melanoma is sometimes found on dark-skinned people, and can often advance more quickly than superficial spreading melanoma and lentigo maligna.
Nodular melanoma is usually invasive at the time it is first diagnosed. The malignancy is recognized when it becomes a bump. It is usually black, but occasionally is blue, gray, white, brown, tan, red or skin tone. This is the most aggressive of the melanomas, and is found in 10 to 15 percent of cases.
Common treatments for metastatic melanoma include chemotherapy, targeted therapies for eligible patients (e.g. BRAF inhibitor treatment for patients with BRAF mutations) and immunotherapy. Metastatic melanoma is a tumor type where immunotherapy has been demonstrated to not only slow disease progression, but to lead to cures in late stage patients. Interleukin-2 was approved for the use in metastatic melanoma in 1998, and in 2011 an antibody targeting CTLA4, a member of a new generation of immune checkpoint inhibitors, gained approval by the FDA.
CDH19 is a type II cadherin transmembrane protein of unknown function. The human gene was cloned in 2000 based on its sequence similarity to CDH7 (Kools, P. et al. Genomics. 2000). Expressed Sequence Tags (ESTs) for CDH19 were isolated from melanocyte cDNA libraries, indicating that expression of CDH19 may be limited to cells of neural crest origin (Kools, P. et al. Genomics. 2000). In support of this notion, rat CDH19 was found to be expressed primarily in nerve ganglia and in Schwann cells during rat embryonic development (Takahashi, M. and Osumi, O. Devl Dynamics. 2005.).
Diagnostic antibodies detecting CDH19 in Western Blot, immunohistochemistry or flow cytometry are known in the art and commercially available. Those antibodies comprise poly- and monoclonal antibodies generated in animal hosts.